Android: Overlay with Circle Cutout ViewGroup

CircularProgressBar.java

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.View;

public class CustomCircleProgressBar extends View {
    private Paint paint;
    private final RectF rect = new RectF();

    private float progress = 100f;

    public CustomCircleProgressBar(Context context) {
        super(context);
        init();
    }

    public CustomCircleProgressBar(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CustomCircleProgressBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }


    void init() {
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(getResources().getColor(R.color.green));

        DisplayMetrics metrics = getResources().getDisplayMetrics();
        int strokeWidth = 8;
        float dpStrokeWidth = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, strokeWidth, metrics);
        paint.setStrokeWidth(dpStrokeWidth);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        float windowWidth = this.getWidth();
        float windowHeight = this.getHeight();

        float edgeOffset = 10;

        rect.set(
                edgeOffset,
                edgeOffset,
                windowWidth - edgeOffset,
                windowHeight - edgeOffset
        );

        float max = 100f;
        float sweep = progress / max * 360;

        canvas.drawArc(rect, -90, sweep, false, paint);
    }

    public void setProgress(final float newProgress) {
        progress = newProgress;
        invalidate();
    }
}

CustomOverlay.java

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

/**
 * This is a ViewGroup that draws an overlay with a circular cutout,
 * and lays out the children in the rectangle around the circular cutout.
 */
public class CustomOverlay extends ViewGroup {
    private Paint paint;
    private Bitmap bitMap;
    private Canvas bitmapCanvas;

    // used to determine children layout with respect to circular cutout.
    // also used to determine if face rectangle is within the circular cutout.
    private final RectF circleBoundingRect = new RectF();


    public CustomOverlay(Context context) {
        super(context);
        init();
    }

    public CustomOverlay(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CustomOverlay(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }


    /**
     * The children are laid out according to the drawing by the parent.
     */
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        // did not draw yet.
        if (circleBoundingRect.top == 0) return;

        // expecting a single child (CustomCircleProgressBar)
        final View child = getChildAt(0);

        child.layout((int) circleBoundingRect.left, (int) circleBoundingRect.top,
                (int) circleBoundingRect.right, (int) circleBoundingRect.bottom);
    }

    private void init() {
        setWillNotDraw(false);
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        if (bitmapCanvas != null) {
            bitmapCanvas.setBitmap(null);
            bitmapCanvas = null;
        }

        if (bitMap != null) {
            bitMap.recycle();
            bitMap = null;
        }

        bitMap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        bitmapCanvas = new Canvas(bitMap);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(bitMap, 0, 0, null);

        float windowWidth = this.getWidth();
        float windowHeight = this.getHeight();


        float cx = windowWidth / 2f;
        float r = windowWidth / 2.5f;
        float cy = windowHeight / 3f;

        float top = (cy - r);
        float bottom = (cy - r) + r * 2;
        float left = (windowWidth - r * 2) / 2;
        float right = ((windowWidth - r * 2) / 2) + r * 2;

        if (top != circleBoundingRect.top ||
                bottom != circleBoundingRect.bottom ||
                left != circleBoundingRect.left ||
                right != circleBoundingRect.right
        ) {
            circleBoundingRect.top = top;
            circleBoundingRect.bottom = bottom;
            circleBoundingRect.left = left;
            circleBoundingRect.right = right;

            // layout children based on new circleBoundingRect
            requestLayout();
        }

        // clear previous overlay draw
        bitmapCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
        // background color
        bitmapCanvas.drawColor(getResources().getColor(R.color.transparent));
        // clear area (cutout)
        bitmapCanvas.drawCircle(cx, cy, r, paint);
    }

    public RectF getFaceRectWithRespectToCustomOverlay(RectF faceRect) {
        RectF rectAdjusted = new RectF(faceRect);
        rectAdjusted.set(
                getWidth() * (1 - faceRect.right),
                (getHeight() * faceRect.top),
                getWidth() * (1 - faceRect.left),
                (getHeight() * faceRect.bottom)
        );

        return rectAdjusted;
    }

    public RectF getCircleBoundingRect() {
        return circleBoundingRect;
    }
}